PSI Setting- Gun or Paint?

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PostPosted: Mon Aug 08, 2022 10:23 pm
I have the Eastwood Concourse 2 gun- it's designed to be used with smaller air compressors. I've sprayed epoxy and primer surfacer with it with good results and I'm getting ready to spray single stage. My Dewalt compressor is having no problem keeping up with the gun.

I'm painting an entire car- bare metal restoration.

My question is about what PSI setting to use. The gun is suggested to be set for 25-30, but the tech sheets for the R-M epoxy says 6-10 for HPLV, the Limco primer surfacer says 8-10 at the cap, and the R-M Uno HD single stage also says to use 8-10 PSI at the air cap for HPLV.

I've read that the pressure at the gun intake (where the gauge is) is higher than at the air cap, but there's no way to measure at the air cap.

The epoxy and P/S both sprayed well at 10 PSI with a 1.7 tip, I'll be using the 1.3 for the single stage.

Advice? Thanks.



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PostPosted: Mon Aug 08, 2022 11:02 pm
The recommended pressure by the gun and paint manufacture are just starting points. what you really need to learn is how to read your spray pattern. if you're getting a rough peely texture then that indicates your air is to low. if your spray is going on smooth but you see a lot of overspray in the room. then you have to much air pressure this can waste a lot of material. the ideal pressure is just enough to get you past that rough orange peel look. I would suggest that you get something to spray some test on before you start on your project.
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PostPosted: Tue Aug 09, 2022 12:04 am
Don't worry about the aircap pressure. It can only be read with special equipment.

Start with your inlet pressure as specified for your gun. Then do a series of test sprays until you get the pattern right, as Jay suggests, above.
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PostPosted: Tue Aug 09, 2022 6:41 am
There is a difference between air pressure (PSI) and air volume (CFM).
Make sure your compressor puts out enough CFM to satisfy your spray gun's needs.
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PostPosted: Tue Aug 09, 2022 2:32 pm
You could even try your test sprays at 20 psi then work your way up.



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PostPosted: Tue Aug 09, 2022 8:40 pm
Thanks guys, Yeah, I'll have to experiment a little before I dare to pull the color trigger on the car. The primers went on OK, the compressor kept up fine (unlike my sandblast cabinet). I started out with the gun a little too far away from the surface ("dry"), but when I found the "sweet spot" I got a good medium wet spray.

It just seemed funny to me that all three tech sheets suggested 8-10 psi at the HVLP gun, whereas most of what I see and read suggests pressures between 20 and 30 for most applications?

EDIT: I think this is close to answering my question- it's from an Eastwood article:

"We recommend painting between 25-30 psi while the trigger is pulled. You may see some paint tech sheets which refer to a painting air pressure of 8-10. Don’t set the spray gun to those as this measurement is referring to the air cap pressure right where the paint comes out. This is a measurement that only the paint gun manufacture has the gauge to read. But by setting your spray gun to the recommended 25-30 PSI at the base you will achieve proper air cap pressure."

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